1. Field of the Invention
This invention generally refers to examining circuit boards and particularly to a method for determining the quality of plated-through holes in circuit boards.
2. Description of the Prior Art
At the present time there is no other reliable method of examining the plating of circuit boards than to mold test holes in plastic and to grind out a surface along the diameter of a hole. The thickness of the applied metal, notably a copper layer, can then be measured and the quality determined. The disadvantage of the method used up to now is that it requires comparatively large amounts of plastic, the greater part of which must be ground away, which becomes both tedious and expensive.
It is also known in the prior art in surface grinding of different types of material for structural examination to mold said material into an appropriate compound, whereafter the entire body is placed in a fixture for grinding. The fixture for the body to be ground can be structured in different ways, for example in accordance with the description of Danish Pat. No. 125 217 (corresponding to the U.S. Pat. No. 3,763,611 and British Pat. No. 1,352,932), wherein the body to be ground is cylindrical and is provided with a circular flange which engages a correspondingly formed surface of the fixture. In this case, too, a substantial quantity of molding material will have to be ground away.